Characteristics
The vessels are designed to be used for scientific research. They might also be used to assist in submarine rescue operations, although they do not have the capacity to take anybody aboard when underwater. The carrier and command centre of both Mir submersibles is the R/V Akademik Mstislav Keldysh. Currently the two Mir units are operated by the Russian Academy of Sciences.
The MIR submersibles can dive to a maximum depth of 6,000 metres (19,685 ft). This makes them two of only seven manned submersibles in the world that can dive beyond 3,000 metres (9,843 ft), the others being the US submersibles Alvin, Sea Cliff and Deepstar 20000, the Japanese owned Shinkai and the French owned Nautile. Up to 98% of the world’s oceans are no deeper than 6,000 metres. All these deep-ocean submersibles utilize three-person crews.
Traditionally, the personnel sphere of a deep sea submersible is manufactured of titanium plates that are welded together. On Mir, the personnel sphere is made of a maraging steel alloy that has 10% better strength/weight ratio than titanium. This alloy contains about 30% cobalt and smaller amounts of nickel, chrome and titanium. Two hemispheres were made by casting and machining, and then bolted together, thus avoiding welded joints. The resulting construction is close to the density of water, thus making it easier to move in different depths. Additional buoyancy is provided by 8 cubic metres (280 cu ft) of syntactic foam. Unlike other Deep Submergence Vehicles that use iron ballast to reach the ocean floor, the buoyancy and depth is adjusted by ballast tanks.
- The Mir is 7.8 m long, 3.6 m wide, 3.0 m high, and weighs 18,600 kg (maximum payload is 290 kg). The personnel sphere's walls are 5 cm thick, and the inside diameter of the working area is 2.1 m. Three viewports are provided (viewport material is 18 cm thick): the forward-facing port is 20 cm diameter; the two side-facing ports are 12 cm diameter each.
- Power is provided by NiCad batteries of 100 kWh capacity. Electric motors drive hydraulic pumps to actuate hydraulic manipulators and 3 propulsors. The aft hydraulic propulsor is rated at 9 kW and 2 side propulsors are rated at 2.5 kW each. Maximum underwater speed is 5 knots.
- Longitudinal trim is controlled using 2 spherical water ballast tanks, fore and aft. Water can be forced out of these tanks as required by using compressed air.
- Air pressure inside the cabin remains at a constant one atmosphere: the air is recycled in a manner similar to that used on board spacecraft, with lithium hydroxide scrubbers removing accumulated carbon dioxide.
- VHF radio is used to maintain communication with the surface. The units contain imaging sonar units of 250 metre range, so nearby objects can be visualized and their distance measured. The distance to the seabed can also be accurately measured when nearing touchdown.
- The units' life-support systems have 246 man-hour capacity, or 3.42 days for a three-person crew.
- The units are designed for pressure at 6,000 metre depth, and have been tested to 125% of that pressure. In field testing, Mir-1 descended to 6,170 m and Mir-2 descended to 6,120 m.
- Originally the hydraulic manipulators were covered by a helmet-like retractable see-through visor, but these were removed in a major overhaul in 1994.
- Mir changes depth at a maximum vertical speed of 40 m per minute, so several hours are required to travel to and from deep sites.
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